This study is primarily aimed at transplanting catecholamine- containing tissues, including adrenal medulla, tumor cells, and embryonic brain tissue, into the brain. Its purpose is to elucidate the properties of these tissues after transplantation and the response of the host brain to the transplanted tissues. Specifically, these experiments employ non-primate animal models to (1) develop the techniques of brain tissue transplantation for clinical use in Parkinson,s disease; (2) develop brain tissue transplantation techniques so they eventually may be applicable to other disorders, such as schizophrenia and e#ilepsy, if and when these disorders become well enough understood to permit such applications; and (3) elucidate factors that control the development and the responses of the brain to injury or impairment, with particular emphasis on the nigrostriatal dopamine system. During the past reporting year, significant progress has been made in these areas.